1. Field of the Invention
The present invention relates to injectors, including for example fuel injectors, having two or more solenoid coils that are provided to reciprocally move an armature connected to a valve and more specifically, relates to injectors having an integrally formed common cylinder that comprises alternating non-magnetic and magnetic portions.
2. Description of the Related Art
In known injectors, an electromagnetic force generated by a solenoid coil controls the opening and closing of a valve. When current is supplied to the solenoid coil, the valve moves to the open position as a result of the electromagnetic force acting on a magnetic armature that is coupled to the valve. A spring disposed within the injector causes the valve to return to the closed position when the current is stopped. However, known injector valves do not quickly return to the closed position after the current is stopped, because the return biasing force of the spring is generally insufficient to quickly close the valve.
In Japanese Patent Laid-Open Publication No. 7-239050 a second solenoid coil is provided to assist in controlling the position of the fuel valve. FIG. 8 herein represents relevant aspects of the injector taught by FIG. 12 of JP 7-239050. As shown in FIG. 8, two solenoid coils S1 and S2 are coaxially disposed in corresponding valve-open and valve-closed positions with respect to the movable armature 86. The armature 86 is coupled to the fuel valve 85 and thus moves together with the fuel valve 85. When current is supplied to solenoid coil S1, the electromagnetic force generated by solenoid coil S1 forces the movable armature 86 towards the valve-opening direction and the fuel valve 85 moves into the open position. When current is supplied to solenoid coil S2, the electromagnetic force generated by solenoid coil S2 forces the movable armature 86 toward the valve-closing direction. Moreover, a spring (not shown) is provided to assist in biasing the fuel valve 85 toward the valve-closed position. Thus, the combined force of the spring and the electromagnetic force of solenoid S2 acting on the movable armature 86 causes the fuel valve 85 to quickly return to the valve-closed position.
As further shown in FIG. 8, a first magnetic path 80 causes the movable armature 86 to move towards the valve-open position and a second magnetic path 87 causes the movable armature 86 to move towards the valve-closed position. In order to adequately control the valve opening/closing operation, the two magnetic paths must be magnetically insulated from each other. Consequently, according to JP 7-239050, a first inner core 81 is disposed on the inner side of solenoid coil S1 and a corresponding first outer core 82 is disposed on the outer side of solenoid coil S1. Moreover, a second inner core 84 is disposed on the inner side of solenoid coil S2 and a second outer core 83 is disposed on the outer side of solenoid coil S2. A non-magnetic spacer 88 is disposed between the first outer core 82 and the second outer core 83 in order to magnetically insulate the first magnetic path 80 from the second magnetic path 87. Finally, a non-magnetic clamp 89 fixes the first outer core 82 and the second outer core 83 with the non-magnetic spacer 88 sandwiched between the first, outer core 82 and the second outer core 83.
A recess 90 is provided between the first inner core 81 and the second inner core 84. By disposing the movable armature 86 within this recess 90, the first magnetic path 80 extends from the first inner core 81 over the movable armature 86 to the first outer core 82. Similarly, the second magnetic path 87 extends from the second inner core 84 over the movable armature 86 to the second outer core 83. The axial length of the movable armature 86 is slightly less than the axial length of the recess 90, so that the movable armature 86 can slide within the recess 90. O-rings (not shown) are provided at various locations to seal the fuel passage from solenoid coils S1 and S2 in order to prevent fuel from leaking from the recess 90 and entering solenoid coils S1 and S2.
According to JP 7-239050, the parts related to the first solenoid coil S1 (solenoid coil S1, inner core 81, outer core 82) and the parts related to the second solenoid coil S2 (solenoid coil S2, outer core 83, inner core 84) are positioned and fixed by the clamping member 89 via the spacer 88. Thus, a relatively large number of parts is required to construct the injector and moreover, it is very difficult to precisely position the various parts during the construction of the injector. For example, coaxial positioning of the inner cores 81 and 84 of the respective solenoid coils S1 and S2, or of the outer cores 82 and 83 is especially difficult. As a result of inevitable errors in positioning the various parts, such fuel injectors do not have reliable dynamic properties.
It is therefore an object of the present invention to teach improved injectors.
In one aspect of the present teaching, a common member or cylinder is disposed within an injector and the common cylinder has integrally formed magnetic and non-magnetic portions. In another aspect of the present teachings, injectors having at least two coaxially disposed solenoid coil s are taught and the common cylinder is disposed either inside or outside of the two solenoid coils. A portion of the common cylinder t hat is disposed adjacent to a space between the two solenoid coils is non-magnetic. Such a structure can insulate the magnetic path for the valve-open position from the magnetic path for the valve-closed position.
Because the common cylinder can comprise a single part, the number of parts necessary to construct a two solenoid coil injector can be significantly reduced over the known art. Also, because the solenoid coils are positioned, with respect to a single common cylinder, positioning of the various parts can be precisely performed when assembling the injector. Thus, reliable magnetic paths and reliable performance are now possible for a two solenoid coil injector.
In another aspect of the present teachings, the common cylinder is disposed inside the solenoid coils. Moreover, the common cylinder may preferably further include non-magnetic portions at positions along the common cylinder that correspond to the valve-open position and/the valve-closed position. According to this structure, the magnetic paths formed by the respective solenoid coils can be prevented from forming a short circuit that does not pass over a movable armature, which is coupled to the valve. Moreover, such a common cylinder has a smooth water-tight surface that allows the movable armature to move smoothly with respect to the common cylinder. Further, fuel leaks from the injector can be prevented, because the fuel path is sealed from the solenoid coils by the common cylinder.
Methods are also taught for preparing common cylinders having integrally formed non-magnetic portions. In one aspect, a representative method includes forming a common cylinder by cutting grooves in a magnetic tubular material and filling the grooves with a non-magnetic material. The magnetic and non-magnetic materials are then fused together to form a water tight common cylinder. The common cylinder is machined to remove magnetic portions adjacent to non-magnetic portions and to provide a smooth, precision finished shape for the common cylinder. Thus, a water-tight common cylinder that provides magnetic insulation between the magnetic paths of a first and second solenoid coil is now possible.
Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.